The club paid Croatia Zagreb £3m for the Australian who has headed home, four days after joining the Glasgow club.

Fergus McCann: "We do not expect to see him back"

McCann fears that he will not return, despite the player's insistence to the contrary, and he believes the player's psychological problems to be sudden enough to merit suspicion.

The club is now planning to seek clarification from various parties, including Croatia Zagreb and Viduka's agents International Management Group (IMG).

McCann added: "Marko Viduka had been playing football at the highest level until recently and there was no indication either from the player, Zagreb or IMG of any psychological problems.

"He was offered medical counselling, his parents to be flown to Glasgow from Australia, a change of hotel, a furnished apartment, a car and a driver, an extended Christmas break and a member of Celtic staff with him at all times.

"These offers were all rejected. Marko advised that he was depressed, unhappy, didn't want to play football. He had difficulties in Zagreb but would not elaborate upon them."

Court action

McCann said the prospect of legal action was being considered: "We will want to get several questions answered and clarified in the next few days. Based on his attitude and behaviour in the last few days we do not expect to see him back."

Celtic had gone to great lengths to sign Viduka and were first linked with him in August.

There was then a long delay due to work permit problems, before he arrived in Glasgow to train on Thursday.

On Friday he did not turn up, and on Saturday, the club said he had left Parkhead without kicking a ball.

Viduka's defence

IMG denied this, and in his own statement the player defended his actions: "It would have been relatively easy for me to cover this up for a few weeks, but that would not have been fair on the club, the fans or my family.

"I just hope everyone realises this is not easy for me and appreciates my honesty."

There was also a bizarre development when a Press Association report quoted the club as saying Viduka had checked into an Aberdeen clinic.

On Sunday the club denied issuing such a statement and attempts to locate the clinic failed.

Viduka has promised to return: "I would just ask everyone to be patient while I get back to full fitness as soon as possible."

But IMG football operations manager Bernie Mandich said there was a distinct possibility that the forward could quit the game altogether.